Dissolved in toxic oceans: how an ancient extinction happened

An artist's reconstruction of a phytosaur, an extinct crocodile cousin, surveying a horizon with rising sulphurous plumes from distant eruptions that prompted the Triassic mass extinction. Scientists say rocks on the English coast contain clues of the processes that drove the end-Triassic event that killed as much as a quarter of all life on Earth. (Victor Leshyk/ The New York Times)

NEW YORK: About 200 million years ago, the rocks that became the Palisades cliffs just across the Hudson River from New York formed during volcanic activity that helped rip apart the ancient supercontinent Pangea.

That volcanism helped lead to the birth of the Atlantic Ocean while it also contributed to killing off as much as one-quarter of all life on Earth during the event known as the end-Triassic mass extinction.